While teaching chess in classrooms several years ago, I searched my database for an instructive position in which each side had one rook and one bishop. I introduce one or two pieces in each classroom session and then let the children play with those pieces. For several years, I would introduce the rook and bishop during the third session.
I like this position from Leonhardt -- Mieses, London 1905. Although Black has a two pawn advantage, White has some tricks that could result in a draw. This position formed the core of the lesson for my beginning students this week.
White to move
Beginners need to understand why Black cannot block this check and must move the king.
We reach the critical position. Black faces the loss of an exchange, reducing the material advantage to point-count equality.
Black to move
Black played 52...Kd4, which turns out to be the only winning move.
Saving the rook gives White the opportunity for a theoretical draw.
If 52...Rf4, then 53.Rxe6 Bxe6 54.Kxe6 Kd4 55.Bxf5
A rook against a bishop is a draw with best play. It is relatively easy to find moves that are good enough.
If 52...Re1 53.Bxf5 exf5 54.Kxf5
A rook and bishop against a rook is also a draw with best play, but the stronger side is capable of torturing the weaker. See "Rook and Bishop versus Rook".
The game's conclusion is also instructive, although we did not go through it in chess club.
53.Bxe4 fxe4 54.Kg5 e3 55.Kf4 e2 56.Ra1 e5+ 57.Kg3 Ke3 58.Rb1 e4 59.Kg2 Kd2 60.Rb2+ Kd1 61.Rb1+ Kc2 62.Ra1 Kd2 0-1